Duhem–Quine thesis
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The Duhem–Quine thesis, also called the Duhem–Quine problem, after
Pierre Duhem Pierre Maurice Marie Duhem (; 9 June 1861 – 14 September 1916) was a French theoretical physicist who worked on thermodynamics, hydrodynamics, and the theory of elasticity. Duhem was also a historian of science, noted for his work on the Eu ...
and
Willard Van Orman Quine Willard Van Orman Quine (; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician in the analytic tradition, recognized as "one of the most influential philosophers of the twentieth century". ...
, is that in science it is impossible to experimentally test a
scientific hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obser ...
in isolation, because an
empirical Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences and ...
test of the hypothesis requires one or more background assumptions (also called ''auxiliary assumptions'' or ''auxiliary hypotheses''): the thesis says that unambiguous scientific falsifications are impossible.: "The physicist can never subject an isolated hypothesis to experimental test, but only a whole group of hypotheses" (Duhem)... "Duhem denies that unambiguous falsification procedures do exist in science." In recent decades the set of associated assumptions supporting a thesis sometimes is called a ''bundle of hypotheses''. Although a bundle of hypotheses (i.e. a hypothesis and its background assumptions) ''as a whole'' can be tested against the empirical world and be falsified if it fails the test, the Duhem–Quine thesis says it is impossible to isolate a single hypothesis in the bundle, a viewpoint called confirmation holism.


The substance of the thesis

The Duhem–Quine thesis argues that no scientific hypothesis is by itself capable of making predictions. Instead, deriving predictions from the hypothesis typically requires background assumptions that several other hypotheses are correct — that an experiment works as predicted, or that previous scientific theory is accurate. For instance, as evidence against the idea that the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
is in motion, some people objected that birds did not get thrown off into the sky whenever they let go of a tree branch. Later theories of physics and astronomy, such as classical and
relativistic mechanics In physics, relativistic mechanics refers to mechanics compatible with special relativity (SR) and general relativity (GR). It provides a non-quantum mechanical description of a system of particles, or of a fluid, in cases where the velocities of ...
could account for such observations without positing a fixed Earth, and in due course they replaced the static-Earth auxiliary hypotheses and initial conditions. Although a bundle of hypotheses (i.e. a hypothesis and its background assumptions) ''as a whole'' can be tested against the empirical world and be falsified if it fails the test, the Duhem–Quine thesis says it is impossible to isolate a single hypothesis in the bundle. One solution to the dilemma thus facing scientists is that when we have rational reasons to accept the background assumptions as true (e.g. explanatory scientific theories together with their respective supporting evidence) we will have rational—albeit nonconclusive—reasons for thinking that the theory under test probably is wrong in at least one respect if the empirical test fails.


Example from Galilean astronomy

The work of
Galileo Galilei Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...
in the application of the
telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...
to astronomical observation met with rejection from influential sceptics. They denied the truth of his most startling reports, such as that there were mountains on the moon and satellites around Jupiter. In particular, some prominent philosophers, most notably Cesare Cremonini, refused to look through the telescope, arguing that the instrument itself might have introduced artefacts that produced the illusion of mountains or satellites invisible to the naked eye.Heilbron, John L. Galileo. Oxford University Press, 2010, 195-196. To neglect such possibilities amounted to
underdetermination In the philosophy of science, underdetermination or the underdetermination of theory by data (sometimes abbreviated UTD) is the idea that evidence available to us at a given time may be insufficient to determine what beliefs we should hold in re ...
in which argument for optical artefacts could be urged as being of equal merit to arguments for observation of new celestial effects. On a similar principle in modern times a prevalent view is that " extraordinary claims demand extraordinary proof." In the early 17th century the modern version of the Duhem–Quine thesis had not been formulated, but common sense objections to such elaborate and ad hoc implicit auxiliary assumptions were urged. To begin with, the mechanism of the (Galilean) telescopes had been explained in terms of
geometrical optics Geometrical optics, or ray optics, is a model of optics that describes light propagation in terms of ''rays''. The ray in geometrical optics is an abstraction useful for approximating the paths along which light propagates under certain circumstan ...
and the nature of the objects that they imaged was consistent; for example a distant lake would not resemble a tree when seen through a telescope. The behaviour of telescopes on Earth denied any basis for arguing that they could create systematic artefacts in the sky, such as apparent satellites that behaved in the predictable manner of Jovian moons. Evidence also offered no basis to suggest that they could present yet other, more elaborate artefacts, fundamentally different from the satellites, such as Lunar mountains that cast shadows varying consistently with the direction of Solar illumination. In practice the politics and theology of the day determined the result of the dispute, but the nature of the controversy was a clear example of how different bundles of (usually implicit) auxiliary assumptions could support mutually inconsistent hypotheses concerning a single theory. In terms of either version of the Duhem–Quine thesis it therefore is necessary to study the defensibility of the auxiliary assumptions, together with the primary hypothesis, to arrive at the most viable working hypothesis.


Pierre Duhem

As popular as the Duhem–Quine thesis may be in
philosophy of science Philosophy of science is a branch of philosophy concerned with the foundations, methods, and implications of science. The central questions of this study concern what qualifies as science, the reliability of scientific theories, and the ultim ...
, in reality
Pierre Duhem Pierre Maurice Marie Duhem (; 9 June 1861 – 14 September 1916) was a French theoretical physicist who worked on thermodynamics, hydrodynamics, and the theory of elasticity. Duhem was also a historian of science, noted for his work on the Eu ...
and
Willard Van Orman Quine Willard Van Orman Quine (; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician in the analytic tradition, recognized as "one of the most influential philosophers of the twentieth century". ...
stated very different theses. Duhem believed that ''only in the field of
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...
'' can a single individual hypothesis not be isolated for testing. He says in no uncertain terms that experimental theory in physics is not the same as in fields like
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
and certain branches of
chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
. Also, Duhem's conception of "theoretical group" has its limits, since he states that not all concepts are connected to each other logically. He did not include at all ''a priori'' disciplines such as
logic Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the science of deductively valid inferences or of logical truths. It is a formal science investigating how conclusions follow from premises ...
and
mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...
within the theoretical groups in physics, since they cannot be tested.


Willard Van Orman Quine

Quine, on the other hand, in "
Two Dogmas of Empiricism "Two Dogmas of Empiricism" is a paper by analytic philosopher Willard Van Orman Quine published in 1951. According to University of Sydney professor of philosophy Peter Godfrey-Smith, this "paper ssometimes regarded as the most important in all ...
", presents a much stronger version of
underdetermination In the philosophy of science, underdetermination or the underdetermination of theory by data (sometimes abbreviated UTD) is the idea that evidence available to us at a given time may be insufficient to determine what beliefs we should hold in re ...
in science. His theoretical group embraces ''all'' of human knowledge, including mathematics and logic. He contemplated the entirety of human knowledge as being one unit of empirical significance. Hence all our knowledge, for Quine, would be epistemologically no different from
ancient Ancient history is a time period from the History of writing, beginning of writing and recorded human history to as far as late antiquity. The span of recorded history is roughly 5,000 years, beginning with the Sumerian language, Sumerian c ...
Greek gods The following is a list of gods, goddesses, and many other divine and semi-divine figures from ancient Greek mythology and ancient Greek religion. Immortals The Greeks created images of their deities for many purposes. A temple would house th ...
, which were posited in order to account for experience. Quine even believed that logic and mathematics can also be revised in light of experience, and presented
quantum logic In the mathematical study of logic and the physical analysis of quantum foundations, quantum logic is a set of rules for manipulation of propositions inspired by the structure of quantum theory. The field takes as its starting point an observ ...
as evidence for this. Years later he retracted this position; in his book ''Philosophy of Logic'', he said that to revise logic would be essentially "changing the subject". In classic logic, connectives are defined according to
truth value In logic and mathematics, a truth value, sometimes called a logical value, is a value indicating the relation of a proposition to truth, which in classical logic has only two possible values (''true'' or '' false''). Computing In some progr ...
s. The connectives in a multi-valued logic, however, have a different meaning than those of classic logic. As for
quantum In physics, a quantum (plural quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantizati ...
logic, it is not even a logic based on truth values, so the logical connectives lose the original meaning of classic logic. Quine also notes that
deviant logic Deviant logic is a type of logic incompatible with classical logic. Philosopher Susan Haack uses the term ''deviant logic'' to describe certain non-classical systems of logic. In these logics: * the set of well-formed formulas generated equals th ...
s usually lack the simplicity of classic logic, and are not so fruitful.


Notes


References

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Further reading

* * * * {{DEFAULTSORT:Duhem-Quine thesis Philosophy of science Empiricism Holism Willard Van Orman Quine